The present invention relates to a microwave oven and, more particularly, to a programmable digital control circuit for allowing a user to select a cooking time period, a cooking mode, and a food temperature to be maintained.
Recently, a digital timer has been developed, wherein an oscillation circuit develops reference pulses for counting a selected time period. The digital timer is very useful for constructing a digital controlled microwave oven.
A microwave oven including a digital timer assembly is disclosed in, for example, U.S. Pat. No. 4,011,428 "MICROWAVE OVEN TIMER AND CONTROL CIRCUIT" by Robert D. Fosnough and David F. Bennet, issued on Mar. 8, 1977. However, the conventional digitalized microwave oven has only a digital timer assembly. In microwave heating cooking, it is necessary to control magnetron output energy and a food temperature at a desired value to perform preferred cooking.
Accordingly, an object of the present invention is to provide a digital control circuit for a microwave oven.
Another object of the present invention is to provide a microwave oven including a programmable digital control circuit for controlling a cooking mode, a cooking time period, and a cooking temperature.
Still another object of the present invention is to provide a digital control circuit for a microwave oven, which automatically controls intermittent defrost cooking.
Other objects and further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. It should be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
To achieve the above objects, pursuant to an embodiment of the present invention, a control panel is provided in a microwave oven, which includes numeral keys and function keys for introducing desired information related to a cooking time period, a cooking mode or a mean output level of a magnetron, and a food temperature to be maintained. The information introduced from the control panel is stored in a digital storage means, of which output signals are applied to a digital control circuit for controlling operation of the magnetron.
A temperature sensing means is provided in the microwave oven for monitoring the internal temperature of food while it is being cooked in the microwave oven. A detection output of the temperature sensing means is introduced into the digital control circuit, which compares the detection output with the temperature information stored in the digital storage means for controlling operation of the magnetron.
In a preferred form, the function keys include a defrost switch for conducting defrost cooking. The digital control circuit includes a programmed control circuit associated with the defrost switch for automatically performing intermittent defrost cooking.